Main gears are easier to weather as they do have some moulded details.
As you all aviation experts know, B737 family main gear's outside hubs are painted to
match the fuselage as they are exposed even retracted. So I painted Tamiya "White"
(Gloss) then lightly weathered in center to make it look used. However the inside hubs,
I'm sure the actual planes have same color as the nose gear hub, but everytime I go to
airport, in my eyes, main gear hubs were more dirty and darker, so I used Tamiya
"Neutral Grey" then again, "TWM" "Oil Stain" These main gear turned out great.
Tamiya Grey colors are from "Sky Grey" -> "Light Grey" -> "Neural Grey" -> "Dark Grey"
order, just in case you guys wonder.